Tanning



Patented July 3%, 1929.

UNITED STATES ALLEN ROGERS AND ROBERT YUN H'UA LEE, OF BROOKLYN, NEW YORK.

TANNING.

No Drawing.

This invention relates to tanning; and it comprises a method of tanning utilizing the tanning properties developed by the simple naphthols, (and their substitution products),

5 particularly in the presence of labile metallic salts, such as ferric chloride or uranium acetate; all as more fully hereinafter set forth and as claimed.

Heretofore it has been proposed to utilize naphthols and some of their derivatives as tanning agents, usually in the presence of some additional chemical, such as formaldehyde, reacting with them to form new bodies having more tanning power. The

naphthols per se, however, have not been found satisfactory as tanning agents, as they are comparatively insoluble and have a low tanning power. Certain naphthol sulfonic acids, such, for example, as 1.4 naphthol sulfonic acid, have also been suggested, but

have not been found commercially satisfactory.

We have found, in a general way, the alpha naphthol derivatives to be more satisfactory and to have greater tanning power than the corresponding beta naphthol compounds. We have also found that while a derivative con taining simply a single sulfonic acid group will tan, those containing more than one sulfonic acid group, without ,other groups, do not tan as well. Chlorin or other acid radicals, substituted in the sulfonic derivatives of the naphthols, decrease the tanning power.

However, with multi-sulfonic acid derivatives, advantageous results are attainable if a basic radical, such as an amino group, is also joined to the naphthol derivative. Thus, alpha naphthol derivatives, containing both amino and sulfonic acid groups,

possess desirable tanning properties. Naphthylene derivatives or naphthylamine com-.v pounds, do not, however, possess such tanning properties. It appears that the presence of the hydroxyl group, (OH), of the naphthol, plays an important part, and that, with the sulfonic acid derivatives, the presence of a basic group, such as NH results in a balancing effect which augments the tanning power of the compound; that it is advantageous to have the tanning agent carry all three substituent groups: a hydroxyl, a sulfonic group and an amino group.

We have observed the eflect of theamino Application filed April 18,

group in sulfonic acid derivatives of alpha acids are 2-amino-8-naphthol-6-sulfonic acid,

(gamma acid) 1amino-8-naphthol-4;-sulfonic acid, (S acid); and 2-amino-5-napl1- thol-7-sulfonic acid, (J acid). The presence of an amino radical in disulfonic acids, such, for example, as 1-am.ino-8-naphthol-2: 4-disulfonic acid, (Chicago acid) and 1- amino-8-naphthol-3:6-disulfonic acid, (H acid) is likewise advantageous.

In all of the foregoing examples including alpha-naphthol per se, we find it possible to employ the salts, particularly the sodium salt, in satisfactory tanning baths. Other metallic salts including the ammonium salt, may be used in place of the sodium derivative.

In view of the markedly increased tanning properties obtained by introducing a basic radical, such as the amino group, in the sulfonic acid derivatives, and the decreased tanning effect observed when additional acid groups were introduced, we have reached the conclusion that there is a balancing effect between the acid and basic radicals. When the balance is maintained Within the limits defined by the character of the compounds mentioned above, the tanning properties of the naphthol sulfonic acids are considerably augmented. As noted above, naphthylene or naphthylamine compounds do not possess the same tanning properties. The difference may be attributed to the presence of a single naphthol radical in the compound, to which is attached an amino group. It has been observed that the secondary or tertiary amines, characterized by the structure =NH or EN, do not balance the sulfonic acid derivatives of the naphthols to the same degree as the primary amine group.

Aromatic substitution products of the naphthol sulfonic acids, also containing an aminogroup, have been found to be desirable tanning agents. Examples of these compounds are phenyl-Q-amino-S-naphthol-6- sulfonic acid, (phenyl gamma mad); and

phenyl-2-amino-5-naphthol-7-sulfonic acid, (phenyl J acid) or their salts. I

In the case of all of the foregoing compounds, which will be recognized as alpha naphthols, an augmented tanning effect can be obtained by adding a little ferric chloride, uranium acetate, or other labile salt.to an aqueous tanning bath of the naphthol. Not only do these salts increase the tanning properties of the alpha naphthols, but they im part desirable tanning properties to the beta naphthols, which alone possess substantially no tanning power. Ferric chloride, in suitable concentrations, may be used alone as a tanning agent, and such use is well known. Its effect in the presence of the naphthols is, however, quite different. The specific behavior in this instance is not clear, but it has been observed that the iron salt does not, of itself, produce tanning. Thus, when employed to give an ordinary iron tannagc, about four per cent of iron as oxide is found in the finished pelt. \Vhen used to increase the tanning properties of the naphthols, the iron remaining as oxide is less than one per cent, and may be as low as 0.25 or 0135 per cent.

As an additional index to the action of ferric chloride, it may be noted that alpha naphthol, which per so will tan only in an alcoholic solution, and beta naphthol, and its derivatives, which will not tan at all in either alcoholic or a ueous solutions, tan well when ferric chloride is added. In accordance with the results noted above, in this case, alpha naphthol gives better results than beta naphthol.

The peculiar behavior of ferric chloride is also exhibited by other labile salts, that is, salts of metals which have several degrees of oxidation. Uranium acetate gives results comparable with those attained with ferric chloride, but it is more expensive. Chronium chloride and aluminum chloride may also be mentioned, but their activity is not as great. Ferric sulfate can be used, but it is inconvenient because of its chemical properties.

Only small amounts of ferric chloride are necessary. to facilitate naphthol tanning.

' The actual amount may range from one part of ferric chloride to about five to twenty parts by weight of organic material, de

pending upon the derivative employed and the nature of the treatment.

Any of the ordina methods of tanning ma be employed. Thus, with the drum me hod, from five to twenty per cent of na hthol, or a derivative, based on the weight of the hides, is dissolved in water, to which may be added 'a little ferric chloride. The volume of the solution is made up to the required amount, usually enough solution be ing employed to float the stock. The pickled hides are put into the drum, which is placed which may be employed. Additional compounds which may be noted are, the sodium salt of 1:5 dihydroxynaphthalene, and 1- naphthol-3:S-disulfomc acid. TThese compounds may be used either with or without ferric chloride or its equivalent. The soluble metallic salts of these derivatives, in-

cluding the ammonium salt may be employed. When the beta na hthol derivatives are used, as, for examp e, Q-naphthol- 8-sulfonic acid, the addition of a converting or catalytic agent, such as ferric chloride, is substantially necessary for commercial operation.

While we have-referred only to naphthols in the foregoing discussion, it is apparent that a balancing efi'ect between such radicals as HSO and NH, attached to cyclic or aromatic compounds containing an OH group, would render such other compounds available for tanning.

lVhat we claim is 1. The rocess of tanning which comprises treating ide with a material containing a simple non-condensed naphthol group in the presence of a labile metal salt, tanning being effected by the concurrent action of the naphthol and salt on each other and on the hide.

2. The process of tanning which comprises treating hide with a material. containing a simple non-condensed a-naphthol group in the presence of a labile metal salt,

process of tanning which comprises treating ide with a material containing a.

simple non-condensed naphthol group in the presence of ferric chloride, tanning being effected by the concurrent action of the naphthol and-chlorid on eachother and on the hide.

4:. The process of tanning which com rises treating ide with a material containing a simple non-condensed a-naphthol group in the presence of ferric chloride, tanning being eficcted by the concurrent action of the naphghgl and chlorid on each other and on the 5. In a process of tanning, the etc which comprises forming a tanning bath 0 a simple non-condensed mono-na hthol derivative including both acid and asic groups.

6. In a process of tanning, the ste which comprises forming a tanning bat of a to increase the tanning power of the said mono-naphthol sulfonic acid, tannin being effected by the concurrent action of t e aro-v matic compound and salt on each other and on the hide.

8. In a process of tanning the step which comprises forming a tanning bath of a simple non-condensed mono-naphthol derivative containing both acid and basic groups and adding thereto a labile metal salt to increase the tanning power of the said simple non-condensed mono-naphthol derivative.

9. In a process of tanning, the step which comprises forming a tanning bath of a mono-naphthol sulfonic acid containing an amino group and adding ferric chlorid thereto to increase the tanning power of the said mono-naphthol sulfonic acid, tanning being effected by the concurrent action of the aromatic compound and salt on each othe and on the hide.

10. In the process of tanning, the step which comprises forming a tanning bath of a simple non-condensed mono-naphthol derivative containing both acid and basic groups and adding ferric chlorid thereto to increase the tanning power of the said simple non-condensed mono-naphthol derivative.

In testimony whereof, we have hereunto affixed our signatures at Brooklyn, New

York, April, 1927.

' ALLEN ROGERS.

ROBERT YUN HUA LEE. 

